Mitosis and Interphase of the Highly Polyploid Palm Voanioalagerardii (2n = 606 ± 3)

The endemic, highly polyploid, monotypic Madagascan palm genus Voanioala (2n ≈ 606) was studied with regard to mitotic stages and interphase. Features of the cell cycle, morphology and sizes of metaphase chromosomes, fluorochrome banding patterns, and silver staining of NORs of such an extremely high polyploid organism are reported for the first time. On a whole, karyokinesis appears to be stable and efficient. A comparison with closely related palm taxa reveals that V. gerardii is 38-ploid, and comparison with the closely related genera Butia, Cocos (coconut) and Jubaea shows that Voanioala has lost ∼ 35% of its DNA amount subsequent to polyploidization and has suppressed between 74 and 88% of the original nucleolar organizers. About 10 active NORs are present in the nuclei. An auto- or allopolyploid origin of Voanioala is discussed with respect to currently available nuclear gene data. The biogeographic relations to Jubaeopsis, a closely related, monotypic, apparently likewise relict palm genus from eastern mainland South Africa are discussed. From a cytogenetic point of view, a common polyploid ancestor of both genera is most likely, but the available molecular phylogenetic data are not univocal.